This application describes experiments to investigate the processes of tumorigenesis and gene regulation in neurons and glia. For these studies, we will use the genes encoding three nervous-system specific intermediate filament proteins: the glial filament acidic protein (GFAP) and two neurofilament (NF) proteins (NF68kd and FF150kd). These genes are abundantly expressed in either astroglia (GFAP) or most neurons (GF68kd, NF150kd) in a developmentally regulated as well as cell type- specific fashion. Specifically, it is proposed to 1) generate neural and glial-specific tumors in transgenic mice by the introduction into germ-line DNA of constructs consisting of NF and GFAP gene promoters (already isolated in the applicant's laboratory) coupled to SV40 T antigen coding sequences. These experiments offer the potential of providing a model of cell type-specific tumorigenesis in the brain. 2) Establish cell lines in culture from such tumors and assay them for the maintenance of NF or GFAP gene expression. Such cell lines would be valuable because of the lack of established neuronally derived lines that maintain a differentiated phenotype. 3) Utilize such cell lines (or others) for the identification and characterization of potential regulatory regions in the NF/GFAP promoters that may bind tissue-specific transcriptional factors using gene transfer experiments and a mobility shift assay; and 4) Investigate the functional significance of the cell type-specific expression of NF's and GFAP by constructing transgenic mice in which the promoters and coding regions of the corresponding genes have been interchanged.